Legislation and statutory regulations require self-monitoring capabilities, for example onboard diagnosis, to monitor motor vehicle emissions of hydrocarbons, carbon monoxide, nitrogen oxides, particulates, and the like. In order to comply with such legal requirements, diagnosis functions are typically integrated within an engine management system for a motor vehicle internal combustion engine. Such management systems typically determine the ongoing performance of exhaust system components such as catalytic converters, nitrogen oxide catalysts, particulate filters and the like.
Currently available diagnostic systems for current and future exhaust aftertreatment systems have significant challenges in attempting to meet future/anticipated statutory emission standards. For example, future diagnostic requirements for diesel engines will require failure detection of a diesel particulate filter (DPF) with a particulate matter deterioration factor as low as 2.5. However, conventional measurement methodologies, for example differential pressure sensors, can only detect particulate matter deterioration factors between 10 to 20. As such, current particulate matter sensor technology does not provide an adequate solution for desired DPF failure detection.
The control and/or detection of non-methane hydrocarbons (NMHC) poses similar challenges to current technology. The detection of NMHC is currently afforded through indirect measurement since NMHC sensors are not available. As such, excessive NMHC emissions are typically tracked through intrusive tests which focus on the exothermic reaction generated during oxidation of the NMHC on a catalytic coating of a catalytic converter and/or DPF. Therefore, an exhaust system that provides for desired DPF failure detection and NMHC monitoring, and yet is simple in design, robust, etc., would be desirable.